Re: Bogus WAL segments archived after promotion

On 04/01/2015 07:12 PM, Bruce Momjian wrote:
> On Fri, Dec 19, 2014 at 10:26:34PM +0200, Heikki Linnakangas wrote:
>> On 12/19/2014 02:55 PM, Heikki Linnakangas wrote:
>>> I'm thinking that we should add a step to promotion, where we scan
>>> pg_xlog for any segments higher than the timeline switch point, and
>>> remove them, or mark them with .done so that they are not archived.
>>> There might be some real WAL that was streamed from the primary, but not
>>> yet applied, but such WAL is of no interest to that server anyway, after
>>> it's been promoted. It's a bit disconcerting to zap WAL that's valid,
>>> even if doesn't belong to the current server's timeline history, because
>>> as a general rule it's good to avoid destroying evidence that might be
>>> useful in debugging. There isn't much difference between removing them
>>> immediately and marking them as .done, though, because they will
>>> eventually be removed/recycled anyway if they're marked as .done.
>>
>> This is what I came up with. This patch removes the suspect segments
>> at timeline switch. The alternative of creating .done files for them
>> would preserve more evidence for debugging, but OTOH it would also
>> be very confusing to have valid-looking WAL segments in pg_xlog,
>> with .done files, that in fact contain garbage.
>>
>> The patch is a bit longer than it otherwise would be, because I
>> moved the code to remove a single file from RemoveOldXlogFiles() to
>> a new function. I think that makes it more readable in any case,
>> simply because it was so deeply indented in RemoveOldXlogFiles.
>
> Where are we on this?

I didn't hear any better ideas, so committed this now.

- Heikki